Kip Stephen Thorne (born June 1, ) is an American theoretical physicist known for his contributions in gravitational physics and astrophysics.A longtime friend and colleague of Stephen Hawking and Carl Sagan, he was the Richard P. Feynman Professor of Theoretical Physics at the California Institute of Technology (Caltech) until and is one of the world's leading experts on the Please contact this domain's administrator as their DNS Made Easy services have expired We would like to show you a description here but the site won’t allow blogger.com more
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Galileo is a global navigation satellite system GNSS that went live in[5] created by the European Union through the European Space Agency ESAoperated by the European Union Agency for the Space Programme EUSPA[6] headquartered in PragueCzech Republic[7] with two ground operations centres in FucinoItaly christine lemaitre dissertation, and Oberpfaffenhofenchristine lemaitre dissertation, Germany.
One of the aims of Galileo is to provide an independent high-precision positioning system so European nations do christine lemaitre dissertation have to rely on the US GPSchristine lemaitre dissertation, or the Russian GLONASS systems, which could be disabled or degraded by their operators at any time.
The higher-precision capabilities will be available for free. Galileo is also to provide a new global search and rescue SAR function as part of the MEOSAR system. The first Galileo test satellite, the GIOVE-Awas launched 28 Decemberwhile the first satellite to be part of the operational system was launched on 21 October By July26 of the planned 30 active satellites including spares were in orbit.
By earlythere were 26 launched satellites in the constellation: 22 in usable condition i. the satellite is operational christine lemaitre dissertation contributing to the service provisiontwo satellites are in "testing" and two more not available to users, christine lemaitre dissertation.
Two test FOC satellites are orbiting the Earth in highly eccentric orbits whose orientation changes with respect to other Galileo orbital planes. Inchristine lemaitre dissertation, the different concepts of the three main contributors of ESA Germany, France and Italy [21] for Galileo were compared and christine lemaitre dissertation to one by a joint team of engineers from all three countries.
The first stage of the Galileo programme was agreed upon officially on 26 May by the European Union and the European Space Agency. The system is intended primarily for civilian use, unlike the more military-oriented systems of the United States GPSRussia GLONASSchristine lemaitre dissertation China BeiDou. The European system will only be subject to shutdown for military purposes in extreme circumstances like armed conflict.
The European Commission had some difficulty funding the project's next stage, after several allegedly "per annum" sales projection graphs christine lemaitre dissertation the project were exposed in November as "cumulative" projections which for each year projected included all previous years of sales.
The attention that was brought to this multibillion-euro growing error in sales forecasts resulted in a general awareness in the commission and elsewhere that it was unlikely that the program would yield the return on investment that had previously been suggested to investors and decision-makers.
A few months later, however, the situation changed dramatically. European Union member states decided it was important to have a satellite-based positioning and timing infrastructure that the US could not easily turn off in times of political conflict. The European Union and the European Space Agency agreed in March to fund the project, pending a review in which was completed on 26 May The required satellites the planned number is 30 were to be launched between andwith the system up and running and under civilian christine lemaitre dissertation from The christine lemaitre dissertation was for private companies and investors to invest at least two-thirds of the cost of implementation, with the EU and ESA dividing the remaining cost.
The base Open Service is to be available without charge to anyone with a Galileo-compatible receiverwith an encrypted higher-bandwidth improved-precision Commercial Service originally planned to be available at a cost, but in February the high accuracy service HAS providing Precise Point Positioning data on the E6 frequency was agreed to be made freely available, with the authentication service remaining commercial.
Galileo is intended to be an EU civilian GNSS that allows all users access to it. Initially GPS reserved the highest quality signal for military use, and the signal available for civilian use was intentionally degraded Christine lemaitre dissertation Availability. This changed with President Bill Clinton signing a policy directive in to turn off Selective Availability.
Since May the same precision signal has been provided to both civilians and the military. Since Galileo was designed to provide the highest possible precision greater than GPS to anyone, the US was concerned that an enemy could use Galileo signals in military strikes against the US and its allies some weapons like missiles use GNSSs for guidance. The frequency initially chosen for Galileo would have made it impossible for the US christine lemaitre dissertation block the Galileo signals without also interfering with its own GPS signals.
The US did not want to lose their GNSS capability with GPS while denying enemies the use of GNSS, christine lemaitre dissertation. Some US officials became especially concerned when Chinese interest in Galileo was reported, christine lemaitre dissertation. An anonymous EU official claimed that the US officials implied that they might consider shooting down Galileo satellites in the event of a major conflict in which Galileo was used in attacks against American forces.
At first, EU officials did not want to change their original plans for Galileo, but they have since reached the compromise that Galileo is to use different frequencies. This allows the blocking or jamming of either GNSS without affecting the other. One of the reasons given for developing Galileo as an independent system was that position information from GPS can be made significantly inaccurate by the deliberate application of universal selective availability SA by the US military.
GPS is widely used worldwide for civilian applications; Galileo's proponents argued that civil infrastructure, including aircraft navigation and landing, should not rely solely upon a system with this vulnerability. On 2 Maythe selective availability was disabled by the President of the United States, Bill Clinton ; in late the entity managing the GPS confirmed that it did not intend to enable selective availability ever again.
As old satellites are replaced in the GPS Block III programme, selective christine lemaitre dissertation will cease to be an option, christine lemaitre dissertation. In Junein a signed agreement with the United States, the European Union agreed to switch to a Binary offset carrier modulation 1, christine lemaitre dissertation. The European Union also agreed to address the "mutual concerns related to the protection of allied and US national security capabilities".
The first experimental satellite, GIOVE-Awas launched in December and was followed by a second test satellite, GIOVE-Blaunched in April After successful completion of the In-Orbit Validation IOV phase, christine lemaitre dissertation, additional christine lemaitre dissertation were launched. On 30 Novemberthe 27 EU transport ministers involved reached an agreement that Galileo should be operational by[36] but later press releases suggest it christine lemaitre dissertation delayed to In mid, the public-private partnership fell apart, and the European Commission decided to nationalise the Galileo programme.
In earlythe EU had yet to decide how to pay for the system and the project was said to be "in deep crisis" due to lack christine lemaitre dissertation more public funds. European Union research and development projects could be scrapped to overcome a funding shortfall. In Novemberit was agreed to reallocate funds from the EU's agriculture and administration budgets [41] and to soften the tendering process in order to invite more EU companies, christine lemaitre dissertation.
In Aprilchristine lemaitre dissertation EU transport ministers approved the Galileo Implementation Christine lemaitre dissertation. In Junethe European Court of Auditors published a report, pointing out governance issues, substantial delays and budget overruns that led to project stalling inleading to further delays and failures, christine lemaitre dissertation.
In Octoberthe European Commission cut the number of satellites definitively planned from 28 to 22, christine lemaitre dissertation, with plans to order the remaining six at a later time. It also announced that the first OS, christine lemaitre dissertation, PRS and SoL signal would be available inand the CS and SOL some time later.
In Novembera ground station for Galileo was inaugurated near Kourou French Guiana. In DecemberEU ministers in Brussels voted Praguein the Czech Republicas the headquarters of the Galileo project. In that same month, Wikileaks revealed that Berry Smutny, the CEO of the German satellite company OHB-Systemsaid that Galileo "is a stupid idea that primarily serves French interests".
The first two Galileo In-Orbit Validation satellites were launched by Soyuz ST-B flown from Centre Spatial Guyanais on 21 October[54] and the remaining two on 12 October Twenty-two further satellites with Full Operational Capability FOC were on order as of 1 January [update]. The first four pairs of satellites were launched on 22 August27 March11 September and 17 December In Januarynews agencies reported that six of the passive hydrogen masers PHM and three of the rubidium atomic clocks RAFS had failed.
Four of the full operational satellites have each lost at least one clock; but no satellite has lost more than two. The operation has not been affected as each satellite is launched with four clocks 2 PHM and 2 RAFS.
The possibility of a systemic flaw is being considered. Additionally some refurbishment is required for the rubidium atomic clocks that still have to be launched. For the passive hydrogen masers operational measures are being studied to reduce the risk of failure. ESA has contacted the Indian Space Research Organisation ISRO who initially reported not having experienced similar failures.
In Julythe European Commission reported that the main causes of the malfunctions have been identified and measures have been put in place to reduce the possibility of further malfunctions of the satellites already in space.
From 11 July till 18 Julythe whole constellation experienced an "unexplained" signal outage [69] [70] with all active satellites showing "NOT USABLE" status on the Galileo status page. On 14 Decemberstarting at UTC, Galileo experienced a system-wide performance degradation lasting for 6 hours.
The problem was related to an abnormal behaviour of a ground segment atomic clock in the time determination function of the system. In SeptemberChina joined the Galileo project, christine lemaitre dissertation.
In JulyIsrael signed an agreement with the EU to become a partner in the Galileo project, christine lemaitre dissertation. On 3 Junethe European Union and Ukraine signed an agreement for Ukraine to join the project, as noted in a press release. In mid, the public—private partnership fell apart and the European Commission decided to nationalise Galileo as an EU programme.
On 30 Novemberthe 27 member states of the European Union unanimously agreed to move forward with the project, with plans for bases in Germany and Italy, christine lemaitre dissertation. Spain did not approve during the initial vote, but approved it later that day. This greatly improved the viability of the Galileo project: "The EU's executive had previously said that if agreement was not reached by Januarythe long-troubled project would essentially be dead".
Christine lemaitre dissertation, while not a member of the EU, christine lemaitre dissertation, is a member of ESA. As a member of ESAit already collaborated in the development of the Galileo satellites, christine lemaitre dissertation, contributing the state-of-the-art hydrogen-maser clocks.
Switzerland's financial commitment for the period — will be calculated in accordance with the standard formula applied for the Swiss participation in the EU research Framework Programme.
In Marchthe European Commission announced that the United Kingdom may be excluded from parts of the project especially relating to the secured service PRS following its exit from the European Union EU. As a result, Airbus plans to relocate work on the Ground Control Segment GCS from its Portsmouth premises to an EU state. As of[87] the system was scheduled to have 15 satellites operational in and reach full operation in [ needs update ] with the following specifications:, christine lemaitre dissertation.
The system's orbit and signal accuracy is controlled by a ground segment consisting of:. The system transmits three signals: E1 The former Safety of Life service is being re-profiled and it will probably be up to the receiver to assess the integrity of christine lemaitre dissertation signal. ARAIM: Advanced Receiver Autonomous Integrity Monitoring [94]. Each Galileo satellite has two master passive hydrogen maser atomic clocks and two secondary rubidium atomic clocks which christine lemaitre dissertation independent of one other.
Under normal conditions, the operating hydrogen maser clock produces the reference frequency from which the navigation signal is generated. Should the hydrogen maser encounter any problem, an instantaneous switchover to the rubidium clock would be performed. In case of a failure of the primary hydrogen maser the secondary hydrogen maser could be activated by the ground segment to christine lemaitre dissertation over within a period of days as part of the redundant system.
A clock monitoring and control unit provides the interface between the four clocks and the navigation signal generator unit NSU.
It passes the signal from the active hydrogen master clock to the NSU and also ensures that the frequencies produced by the master clock and the active spare are in christine lemaitre dissertation, so that the spare can take over instantly should the master clock fail, christine lemaitre dissertation. The NSU information is used to calculate the position of the receiver by trilaterating the difference in received signals from multiple satellites.
The onboard passive hydrogen maser and rubidium clocks are very stable over a few hours. If they were left to run indefinitely, though, christine lemaitre dissertation, their timekeeping would drift, so they need to be synchronized regularly with a network of even more stable ground-based reference clocks.
These christine lemaitre dissertation active hydrogen maser clocks and clocks based on the caesium frequency standardwhich show a far better medium and long-term stability than rubidium or passive hydrogen maser clocks.
These clocks on the ground are gathered together within the parallel functioning Precise Timing Facilities in the Fucino and Oberpfaffenhofen Galileo Control Centres. The ground based clocks also generate a worldwide time reference called Galileo System Time GSTthe standard christine lemaitre dissertation the Galileo system and are routinely compared to the local realisations christine lemaitre dissertation UTC, the UTC k of the European frequency and time laboratories.
For more information of the concept of global satellite navigation systems, see GNSS and GNSS positioning calculation. The European GNSS Service Centre GSCchristine lemaitre dissertation, [] located in Madrid, is an integral part of Galileo and provides the single interface between the Galileo system and Galileo users.
GSC publishes Galileo official documentation, christine lemaitre dissertation, promotes Galileo current and future services worldwide, supports standardisation and distributes Galileo almanacs, ephemeris and metadata, christine lemaitre dissertation.
The GSC User Helpdesk [] is the point of contact for Galileo user's assistance.
Reflecting on Supervisory Practice with Professor Christine Le Maitre \u0026 Professor Doug Cleaver
, time: 15:46Galilée (savant) — Wikipédia
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